Rotary expansible chamber devices are made up of at least one body that rotates relative to another body and that defines in conjunction with that other body the boundary of a fluid zone that is configured to receive a working fluid during use. The fluid zone is typically comprised of a plurality of fluid volumes that increase and decrease in size as the rotating body rotates. Rotary expansible chamber devices can be used, for example, as compressors, where a compressible fluid enters the plurality of fluid volumes and is compressed as the fluid volumes decrease in size, or the devices can be used as expanders, where the energy from a compressible fluid is transferred to the rotating body as the fluid is allowed to expand within the fluid volumes.
A 360° rotation of the rotating body(ies) of a rotary expansible chamber device can be divided into a number of arcs, each of which describes one of the following three categories: a) a shrinking arc, in which the volume of the working fluid partially or fully bounded by the body(ies) is shrinking, b) an expanding arc, in which the volume of fluid partially or fully bounded by the body(ies) is expanding, and c) a constant volume arc, in which the volume of fluid partially or fully bounded by the body(ies) is not changing in size. These arcs may or may not move with some relation to the rotating body(ies). At locations generally relative to these arcs are openings or ports which allow fluid to enter and leave the fluid zone.
An expansible chamber device can have a variety of operating parameters, such as the rotation rate of the device, the mass flow rate of a working fluid, the working fluid output temperature and pressure, and the energy either produced or consumed by the device. However, prior art devices are poorly equipped to control one or more of these parameters independently of the other operating parameters, and are poorly equipped to do so in an energy efficient manner.